In the past, communication using time division multiplexing systems has been widely used in many fields. In such time division multiplex communication, one wireless or wired transmission path can be shared by time division multiplexing (TDM) multiple channels or circuits. With one type of TDM technology, multiple channels use one shared circuit, so the usage time of that shared circuit is equally divided and allocated in order to multiple channels. One method for equally dividing the usage time is a method where, for example, the usage time is segmented into multiple time slots and one is allocated to each of multiple channels. With this method, the bandwidth of a single circuit is allocated equally to each channel by using time slots in which the information from multiple channels has been allocated to each channel beforehand. In this case, a time slot will be allocated to each channel regardless of whether or not there are data to transmit. Another system of time division multiplex communication includes the asynchronous time division multiplex system. This system also transmits information in the same way as regular time division multiplex communication, but the difference is that this system is that rather than allocating time slots to specific channels beforehand, time slots are allocated as needed. Still another system includes the time division multiple access system that is used in wireless communications, such as for portable telephones, etc. This system is a system where one carrier frequency is shared by multiple receivers and stations, each for a short time.
Concerning the allocation of the transmission path or time slots for using the transmission path in time division multiplex communication systems, in broad terms, a first method is allocation by including the destination address (for example, a device identification code) in the data packet transmitted, a second is allocation by determining the packet arrangement information (time information) in advance and using that arrangement information as the destination information, and a third is allocation by transmitting an allocation signal along with the packet that is transmitted. An example of the first method is Ethernet (registered trademark) (IEEE 802.3), which is often used with LANs, and TCT/IP, which is used with PC networks, etc. These are configured so that the data packets (frames) include destination information. There are also ATM (asynchronous transfer mode) communication networks that have been widely disseminated in broadband communication networks. Here, high transmission bandwidths are maintained by using 53-byte ATM cells as the minimum unit and by allocating the transmission band to any specific equipment as necessary. In this case, since it is asynchronous, the ATM cell is divided into a 5-byte header that includes the leading synchronous bit and a 48-byte payload following that. The beginning and end of the ATM cell is identified by detecting the synchronous bit. The TCP/IP, LAN packets, and the like are also associated with the payload. Examples of the third method generally include microcomputer, DSP, and other memory map (input/output (I/O) map) systems.
Also, in the past there have been several methods for identifying the various devices when there is communication between the devices, such as various integrated circuit chips, units, equipment, etc., in circuits, devices, systems, etc. As one method, there is that in which a characteristic device identifier is used as the device identifier or address for communication in the system. Characteristic device identifiers include, for example, the number printed on the ROM during manufacture in an integrated circuit chip. Standards for using such a characteristic device identifier include the JTAG standard used in testing chip mounting on boards and IIC (example: Audio I/F (IIC)) used in many audio components. A second method includes assigning addresses externally to the branch, leaf device. An example where this method is used is the IEEE 1394 standard. In addition, a third method is where the device identifier, that is, the address, is predetermined by the system. An example of this is the SCSI-2 standard. In this standard, a specific address is recommended in advance by the operating system for devices such as printers, displays, etc.
Time division multiplex communication technology such as the, or time division multiplex communication technology such as time division multiple access technology, is constituted to allocate time slots equally, or to assign them equally to different channels when they are allocated. Thus the amount of information per unit time that each channel is to transmit or the transmission speed is fixed. Therefore, in systems in which multiple channels with different amounts of information or transmission speeds are mixed, the problem arises where efficient or optimal communication will not be accomplished using a single transmission path. Also, time slots are allocated as necessary in asynchronous multiplex systems, so that while the time slots are used efficiently, there is the problem that redundant information, such as the destination address, is included in the transmitted information.
They are also problems such as the following in the methods where the transmission path is allocated to different channels in time division multiplex communication. That is, with the first method, where data such as the destination address are included in the data packet transmitted, information other than the original data to be transmitted must also be included, the transmission efficiency for the original data drops, and all the data packets must always be monitored so that all the destination addresses are sent. With the second allocation method where the packet arrangement information is determined beforehand, the packet arrangement order must again be changed according to the destination address arrangement to accommodate changes to the system structure. Because of this, system connections will have to be changed, and programs, etc. will have to be changed, and the problem is that the overall system lacks flexibility. In addition, with the third allocation method, where an allocation signal is transmitted along with the data packet, for example, in a memory map (input/output (I/O) map) system, memory (I/O) space is allocated to all the devices, the device address and a device selection signal are associated, and communication with the destination device will be accomplished by producing a device selection signal for each device. The problems are that this system also lacks system flexibility, and device selection signals are required for the number of devices.
In addition, in the case of the first method, where the characteristic device identifier is used as the device identification method, particularly in the case of integrated circuit chips, the characteristic identifier is dependent on the device manufacturer, the type, such as the device function, etc, and a characteristic device different device identifier is allocated to devices manufactured by different manufacturers, even when they are the same type of device. Because of this, in systems such as audio components, it is not possible to simply replace, the device used with a device from a different manufacturer, even if it is the same time of device. To accomplish such a replacement, the device identifier of the device in the system prior to replacement must be replaced by the device identifier of the device after replacement. This also includes overwriting the software, overwriting the ROM contents, etc. Another problem is that, in order to use several of the same type of device in a system, devices with the same device identifier cannot be used, so that multiple device identifiers are printed on the ROM for one device as a countermeasure, and it must be possible to select one of them when a device is used. In addition, in systems that require other device identifiers instead of characteristic device identifiers, new identifiers or addresses must be given for the device. On the other hand, with the second method for device identification, an address must be assigned externally for a device, so that software and hardware for giving that address is required. With the third method for device identification, an address used by a specific device is preset in the operating system, so there are restrictions on address assignment. There are also restrictions on the number of devices that can be connected to the system.
Thus the purpose of this invention is to provide a time division multiplex transmission method and device that transmits information on multiple channel using a transmission path with variable time division multiplexing.
Another purpose is to provide a variable time division multiplex communication method and device that can automatically assign the sequence of time slots in allocation order to multiple channels for transmitting over the transmission path.